The present invention is for use with an internal combustion engine. In such engines, the air in the crankcase builds up a certain overpressure and must be released. However, release may not be in any way whatsoever. The air must first be cleaned. Up until now, cleaning has been by attempting to combust the contaminated crankcase air after it has been led from the crankcase back into the engine's inlet manifold. However, this has had certain disadvantages for the engine. Carbon coating is one example of such a disadvantage.